Prioritized random access for magnetic recording

ABSTRACT

A storage device includes a controller that directs incoming data to a storage location based on a capacity of a region or surface of a magnetic disc. According to one implementation, the storage device controller writes new data to data tracks in a first series of data tracks on the magnetic disc until a capacity condition is satisfied. Once the capacity condition is satisfied, the storage device controller writes new data to a second series of data tracks on the storage medium that are interlaced with data tracks of the first series.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/699,834, entitled “Prioritized Random Access for MagneticRecording” and filed on Apr. 29, 2015, which claims benefit of priorityto U.S. Provisional Application No. 62/083,696, entitled “InterlacedMagnetic Recording in HAMR Devices” and filed on Nov. 24, 2014; U.S.Provisional Patent Application No. 62/083,732, entitled “InterlacedMagnetic Recording” and filed on Nov. 24, 2014; and also to U.S.Provisional Patent Application No. 62/097,416, entitled “PrioritizedRandom Access for Magnetic Recording” and filed on Dec. 29, 2014. Eachof these applications is specifically incorporated by reference for allthat it discloses or teaches.

BACKGROUND

As requirements for data storage density increase for magnetic media,cell size decreases. A commensurate decrease in the size of a writeelement is difficult because in many systems, a strong write fieldgradient is needed to shift the polarity of cells on a magnetizedmedium. As a result, writing data to smaller cells on the magnetizedmedium using the relatively larger write pole may affect thepolarization of adjacent cells (e.g., overwriting the adjacent cells).One technique for adapting the magnetic medium to utilize smaller cellswhile preventing adjacent data from being overwritten during a writeoperation is shingled magnetic recording (SMR).

SMR allows for increased areal density capability (ADC) as compared toconventional magnetic recording (CMR) but at the cost of someperformance ability. As used herein, CMR refers to a system that allowsfor random data writes to available cells anywhere on a magnetic media.In contrast to CMR systems, SMR systems are designed to utilize a writeelement with a write width that is larger than a defined track pitch. Asa result, changing a single data cell within a data track entailsre-writing a corresponding group of shingled (e.g., sequentiallyincreasing or decreasing) data tracks.

Therefore, better designs are desired to increase storage deviceperformance while achieving or improving upon the ADC of existing SMRsystems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a data storage device including a transducer headassembly for writing data on a magnetic storage medium.

FIG. 2 illustrates data writes to a magnetic disc employing an exampleprioritized random access (PRA) write scheme in a conventional magneticrecording system.

FIG. 3 illustrates incrementing of write counters for various datatracks 01responsive to a data write to a central data track.

FIG. 4 illustrates data writes to a magnetic disc in an interlacedmagnetic recording (IMR) system.

FIG. 5 illustrates data writes to a magnetic disc employing anotherexample PRA scheme in an IMR system.

FIG. 6 illustrates data writes employing another example PRA scheme inan IMR system.

FIG. 7 illustrates an example multi-phase write management method forwriting to a region of a magnetic storage medium of an IMR system.

FIG. 8 illustrates another example multi-phase write management methodfor writing to a region of a magnetic storage medium of an IMR system.

FIG. 9 illustrates example operations for employing a PRA scheme in anIMR system.

FIG. 10 illustrates example operations for employing another example PRAscheme.

SUMMARY

Implementations disclosed herein provide for a storage device controllerconfigured to write new data to data tracks in a first series of datatracks on a storage medium until a first capacity is satisfied. Once thecapacity condition is satisfied, the storage device controller writesnew data to data tracks in a second series of data tracks on the storagemedium. Each of the data tracks of the second series of data tracks isinterlaced between data tracks of the first series.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. These andvarious other features and advantages will be apparent from a reading ofthe following Detailed Description.

DETAILED DESCRIPTION

FIG. 1 illustrates a data storage device 100 including a transducer headassembly 120 for writing data on a magnetic storage medium 108. Althoughother implementations are contemplated, the magnetic storage medium 108is, in FIG. 1, a magnetic storage disc on which data bits can berecorded using a magnetic write pole (e.g., a write pole 130) and fromwhich data bits can be read using a magnetoresistive element (notshown). As illustrated in View A, the storage medium 108 rotates about aspindle center or a disc axis of rotation 112 during rotation, andincludes an inner diameter 104 and an outer diameter 102 between whichare a number of concentric data tracks 110. Information may be writtento and read from data bit locations in the data tracks on the storagemedium 108.

The transducer head assembly 120 is mounted on an actuator assembly 109at an end distal to an actuator axis of rotation 114. The transducerhead assembly 120 flies in close proximity above the surface of thestorage medium 108 during disc rotation. The actuator assembly 109rotates during a seek operation about the actuator axis of rotation 112.The seek operation positions the transducer head assembly 120 over atarget data track for read and write operations.

The transducer head assembly 120 includes at least one write element(not shown) that further includes a write pole for converting a seriesof electrical pulses sent from a controller 106 into a series ofmagnetic pulses of commensurate magnitude and length. The magneticpulses of the write pole selectively magnetize magnetic grains of therotating magnetic media 108 as they pass below the pulsating writeelement.

View B illustrates magnified views 114 and 116 of a same surface portionof the storage media 108 according to different write methodologies andsettings of the data storage device 100. Specifically, the magnifiedviews 114 and 116 include a number of magnetically polarized regions,also referred to herein as “data bits,” along the data tracks of thestorage media 108. Each of the data bits (e.g., a data bit 127)represents one or more individual data bits of a same state (e.g., 1s or0s). For example, the data bit 128 is a magnetically polarized regionrepresenting multiple bits of a first state (e.g., “000”), while theadjacent data bit 127 is an oppositely polarized region representing oneor more bits of a second state (e.g., a single “1”). The data bits ineach of the magnified views 114 and 116 are not necessarily illustrativeof the actual shapes or separations of the bits within an individualsystem configuration.

The magnified view 114 illustrates magnetic transitions recordedaccording to a conventional magnetic recording (CMR) technique. In a CMRsystem, all written data tracks are randomly writeable and ofsubstantially equal width.

According to one implementation, aspects of the disclosed technology areimplemented in a CMR system to improve drive performance. In particular,certain aspects of the disclosed technology provide for directed writesto specific data tracks based on a drive or region capacity. The same orother aspects of the disclosed technology may also be implemented innon-CMR systems such as an interlaced magnetic recording (IMR) systemexemplified in the magnified view 116.

The IMR system shown in the magnified view 116 illustrates alternatingdata tracks of two different written track widths. A first series ofalternating tracks (e.g., the tracks 158, 160, and 162) have a widerwritten track width than a second series of interlaced data tracks(e.g., 164 and 166). In one implementation, each data track of the firstseries of alternating data tracks (e.g., the data track 160) is writtenbefore the immediately adjacent data tracks of the second series (e.g.,164 and 166).

According to one implementation, data of the second series (e.g., 164,166) is of a lower linear density (e.g., along-track density) than dataof the first series (e.g., 158, 160, and 162). Other implementationsutilize more than two different linear densities to write data. The IMRtechnique illustrated in the magnified view 116 provides for a highertotal areal density capability (ADC) with a lower observable bit errorrate (BER) than CMR systems.

To write new data to the magnetic storage medium 108, a storagecontroller 106 of the storage device 100 selects a storage locationbased according to a number of prioritized random access (PRA) rules.For example, the controller 106 selects storage locations for eachincoming write command to systematically maximize a total number ofpossible random writes, to improve drive performance, etc. If the system100 is a CMR system, the storage controller 106 may write data tracks inan order that maximizes a number of random writes on the storage medium108. If the system 100 is an IMR system, the storage controller 106 maywrite to different (e.g., interlaced) data tracks on the magneticstorage medium 108 with different linear densities and written trackwidths.

In at least one implementation, the storage medium 108 is dividedradially into zones and each zone is associated with multiple lineardensities and/or written track widths. For example, two or moredifferent linear densities may be used to write data of alternatingtracks within each individual radial zone. The linear densities employedin one radial zone may differ from the linear densities employed in anyother radial zone of the storage medium 108.

The controller 106 includes software and/or hardware, and may beimplemented in any tangible computer-readable storage media within orcommunicatively coupled to the storage device 100. The term “tangiblecomputer-readable storage media” includes, but is not limited to, RAM,ROM, EEPROM, flash memory or other memory technology, CDROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other tangible medium which can be used to store the desiredinformation and which can be accessed by mobile device or computer. Incontrast to tangible computer-readable storage media, intangiblecomputer-readable communication signals may embody computer readableinstructions, data structures, program modules or other data resident ina modulated data signal, such as a carrier wave or other signaltransport mechanism. The term “modulated data signal” means a signalthat has one or more of its characteristics set or changed in such amanner as to encode information in the signal.

FIG. 2 illustrates data writes in magnetic disc 200 employing an examplePRA write scheme in a CMR system. The magnetic disc 200 includes anumber of substantially circular data tracks (e.g., data tracks 202,210). A controller (not shown) selects data tracks to receive and storeincoming data. For each write operation, the controller identifiesrelevant PRA rules and executes the write operation in a manner thatsatisfies the identified PRA rules.

In general, PRA rules define a write priority among data in various datatracks. In the example of FIG. 2, an example implemented PRA rulespecifies that every-other data track is left blank for a period of timeas the magnetic disc 200 begins to fill up with data. In oneimplementation, new data is written to alternating data tracks (asshown) until a capacity condition is satisfied. A capacity condition maybe, for example, a set capacity of the magnetic storage medium of aradial zone on the medium (e.g., 50% or more). In other implementations,PRA rules may apply other capacity conditions. For example, one PRA rulespecifies that data can be written to data track 204 as soon as data iswritten to the data tracks 203 and 205.

One advantage to writing data exclusively to alternating data tracks (asshown) is that a risk of adjacent track interference (ATI) (alsoreferred to as adjacent track erasure (ATE)) is substantiallyeliminated. For example, a write of new data to a data track 205 cannotinterfere with data in the adjacent tracks 204 and 206 if those adjacenttracks are left blank (as shown).

In some perpendicular recording devices, a wide write field generated bya write head causes side track erasure (STE). STE refers to the erasureof data on a data track that is not immediately adjacent to the datatrack subject to a write operation causing the erasure. For example, STEmay refer to erasure of data in the data track 206 during a writeoperation to the data track 204. The effect of STE is prevalent in avariety of types of storage devices, but does not exist in heat-assistedmagnetic recording (HAMR) devices. Therefore, the illustratedimplementation (which eliminates ATI) is particularly useful when usedin conjunction with a HAMR storage device (which further eliminatesSTE).

Some recording devices regularly perform certain processing operationsto monitor data degradation attributable to ATI and STE. For example, astorage device controller may regularly read back data tracks or datasegments to measure degradation of the stored data. In general, a smalldegree of data degradation may be acceptable if the data is repairablevia an error correction code (ECC) of the storage device. However, ifthe degradation becomes too severe, the ECC may be unable to repair thedata.

In one implementation, a storage device controller initiates a directoffline scan (DOS) of a data track after a particular number of datawrites to an immediately adjacent or nearby data track. A DOS is anexample post-write scan operation also referred to as a defective datascan. The purpose of the DOS is to measure degradation to a particulardata track, such as degradation that is due to ATI and STE. During theDOS, data is read back from a data track on storage medium 200. The ECCrepairs errors in the data to the extent possible, and counts a numberof correctable read errors. If the number of correctable read errorsexceeds a threshold, the storage device controller may elect to re-writethe data of that data track before the data degradation becomes moresevere. For example, a DOS may be initiated to read back the data tracks202 and/or 204 after the data track 203 is been updated X number oftimes (e.g., 5 times) without re-writing the data of the data tracks 202and 204. If the DOS indicates that the data tracks 202 and/or 204 aresignificantly degraded, a storage controller may re-write the datatracks 202 and 204.

Due to significant processing overhead, regular and frequent DOSoperations reduce device performance. One implementation of thedisclosed technology improves device performance by reducing a totalnumber of DOSs that are performed while still ensuring a sufficientlevel of stored data integrity. As discussed above, the illustratedwrite methodology (e.g., writing data to every other data track)eliminates the risk of ATI during each write operation. Therefore, DOSscan be performed less frequently or not at all in this system during aperiod of time where data is written exclusively to every other datatrack (as shown).

In FIG. 2, the data tracks each have an identical written track width.However (as will be discussed in greater detail below), this writemethodology may also be applicable to non-conventional magneticrecording systems such as IMR systems.

In one example of the above-described write methodology, data is writtento alternating data tracks across entire surface of the storage media200 before any data is written to the interlaced tracks between thealternating data tracks. During this time, post-write scan operationsare disabled. Once a capacity condition is satisfied (e.g., sized ofstored data is approximately 50% of a disc capacity), the post-writescan operations (e.g., DOS operations) are enabled.

Post-write scan operations include, for example, enabling a writecounter in association with a particular data track; initiating a DOS ofa data track whenever the associated write counter satisfies a counterthreshold; re-writing the data track if the DOS indicates the data trackis significantly degraded; and resetting the write counter for the datatrack when the data track is re-written.

When post-write scan operations are enabled, a write operation to anyparticular data track increases a write counter associated with nearby(e.g., immediately adjacent) data tracks. For example, a write operationdirected to the data track 204 increases a write counter associated withthe data tracks 203 and 205. The more times that the data track 204 iswritten to, the more likely it is that data is corrupted on the adjacentdata tracks 203 and 205.

When the write counter for a particular data track exceeds a threshold,the data track is subjected to a DOS. For example, the data track 203may be subjected to a DOS if an associated write counter exceeds athreshold value. The DOS scans the data track 203, and determineswhether a number of correctable read errors satisfies an errorthreshold. If the number of correctable read errors satisfies the errorthreshold, the storage device controller re-writes the data of the datatrack 203 and resets the write counter of the data track 203 to adefault starting value.

In one implementation, the write methodology illustrated in FIG. 2 isimplemented within a particular radial zone of disc. For example, astorage device controller may use such methodology when writing data toa high performance radial zone near the outer diameter of the storagemedia 200 but not while writing data to a lower performance radial zonenear the inner diameter.

In some implementations, incrementing a write counter entails scaling anentire affected region (e.g., more than just immediately adjacenttracks) by a scalar value to obtain a new increment write count. Forexample, FIG. 3 illustrates incrementing of example write counters 300for various data tracks responsive to a data write to a central datatrack 302. Since the data tracks closest to the central data track 302are at a highest risk of ATI and STE (e.g., if the storage drive is anon-HAMR drive), the write counter for each of the data tracksincrements in proportion to a distance from the central data track 302where the data is written. For example, write counters for the datatracks immediately adjacent to the central data track 302 increment by10; write counters for the data tracks two tracks away from the centraldata track 302 increment by 7; write counters for the data tracks threetracks away from the central data track 302 increment by 4, etc.

A variety of other scaling techniques are also contemplated in additionto that illustrated by FIG. 3. In one implementation, a data write to aparticular data track increments write counters associated with 100adjacent tracks (e.g., −50 tracks and +50 tracks from the central track302). When the write counter for any particular data track exceeds apredetermined threshold, that data track is subjected to a DOS. The DOSscans data of the data track, and determines whether a number ofcorrectable read errors satisfies an error threshold. If the number ofcorrectable read errors satisfies the error threshold, the storagedevice controller re-writes the data of that data track and resets thewrite counter of the data track to a default starting value. In oneimplementation, write counters are not incremented until capacity of amagnetic disc satisfies a capacity condition, such as 50% region or disccapacity.

FIG. 4 illustrates example data writes in an IMR system. The magneticdisc 400 includes a number of substantially circular data tracks (e.g.,data tracks 402-410). A controller (not shown) selects data tracks toreceive and store incoming data.

In FIG. 4, the dotted lines indicate boundaries between adjacent datatracks having a same track pitch 416 (e.g., distance between centers ofadjacent data tracks). In one implementation, a same or substantiallyequal track pitch is employed across an entire surface of the magneticdisc 400. However, the track pitch 416 of each data track is smallerthan a written track width (W1), (e.g., an actual width of recorded databits in the cross-track direction) for data written to a first pluralityof alternating data tracks 404, 405, 407, and 409.

In various implementations, the first plurality of alternating datatracks (e.g., 404, 405, 407, and 409) includes either exclusivelyeven-numbered tracks or exclusively odd-numbered tracks. Tracksinterlaced with the first plurality of alternating data tracks have anarrower written track width (e.g., less than W1) and, by convention,overwrite the edges of data bits stored in the immediately adjacent todata tracks of wider written width.

To simplify nomenclature, the first plurality of data tracks (e.g.,those tracks written with a wider bit footprint) are shown and are alsoreferred to herein as “odd-numbered” data tracks. It should beunderstood, however, that the odd-numbered tracks may, in practice, beeven-numbered tracks and vice versa. In at least one implementation, theinterlaced (e.g., odd-numbered) data tracks are written with a higherlinear density than the even-numbered data tracks.

In one implementation, data is written to alternating data tracks in aregion of the storage media 400 before any data is written to theinterlaced tracks between the alternating data tracks. In FIG. 4, thedata tracks of wider written track width (404, 405, 407, 409) arewritten to before the interlaced tracks of narrower written track width(e.g., 402, 404, 406, 408, and 410). So long as there is a spacing(e.g., a blank track) between each data track including data, there isno risk of data loss due to ATI.

As discussed above with respect to FIG. 2, this type of writemethodology allows for disabling of post-write scan operations for aperiod of time as the magnetic disc 400 begins to fill up. Once themagnetic disc 400 or a particular radial zone of the disc 400 reaches apredetermined capacity (e.g., satisfies a capacity condition), thepost-write scan operations are enabled. While the post-write scanoperations are enabled, a write operation to any particular data trackincreases a write counter associated with two or more adjacent datatracks.

When the write counter for any particular data track exceeds apredetermined threshold, that data track is subjected to a DOS. The DOSscans data of the data track and determines whether a number ofcorrectable read errors satisfies an error threshold. If the number ofcorrectable read errors satisfies the error threshold, the storagedevice controller re-writes the data of that data track and resets thewrite counter of the data track to a default starting value.

The illustrated write methodology may be used to write data to an entiresurface of the magnetic disc 400 or one or more individual radial zoneon the magnetic disc 400. The capacity condition for enabling thepost-write DOS scan for a particular region (e.g., the radial zone orsurface of the magnetic disc 400) may be satisfied when, for example, asize of data stored in the region is 50-65% of a total capacity of theregion. In IMR systems, capacity within a region can be unevenlydistributed between consecutive data tracks (e.g., if the various datatracks store data of different respective linear densities). Therefore,a region on the magnetic disc 200 may store greater than 50% of thetotal capacity of the region without storing any data in the blank,interlaced data tracks (e.g., 402, 404, 406, etc.).

In one implementation, the storage device controller sequentially writesdata to the alternating data tracks 403, 405, 407, 409, etc. asindicated by the notation “write 1”, “write 2”, “write 3”, and “write 4”at the bottom of FIG. 4. In another implementation, writes to thealternating data tracks 403, 405, 407, 409, etc. are in a differentorder.

In an implementation where post-write scan operations are disabledduring writes to alternating data tracks (as discussed above), deviceperformance improves as compared to an implementation that performs oneor more post-write scan operations (e.g., incrementing a write counter)after every write operation to allow for periodic integrity checks ofstored data

The illustrated write methodology also has the added benefit ofpermitting all write operations to be performed at random until thepoint in time where the storage device controller begins to write datato the interlaced (e.g., even-numbered) data tracks.

Other implementations of the disclosed technology, discussed below,utilize other PRA rules for data management. These rules may be utilizedalone or in conjunction with the post-write DOS disabling rule discussedabove.

FIG. 5 illustrates example data writes to a magnetic disc 500 employinganother PRA scheme in an IMR system. The magnetic disc 500 includes anumber of circular data tracks (e.g., data tracks 502-510). A controller(not shown) selects data tracks to receive and store incoming data. Inone implementation, the controller directs the incoming data writes to aseries of alternating data tracks (e.g., odd-numbered data tracks 503,505, 507, and 509) for a period of time until a first capacity conditionis satisfied. During this time period, data tracks interlaced (e.g., theeven-numbered data tracks) with the alternating data tracks are leftblank.

In FIG. 5, a written track width W2 of the even-numbered data tracks isless than or approximately equal to a defined track pitch 516 (e.g., aspacing between a center of an even-numbered data track and an adjacentodd-numbered data track). A written track width W1 of the odd-numbereddata tracks is greater than the defined track pitch 516. In oneimplementation, a ratio of track width of odd-numbered data tracks tothe track width of even-numbered data tracks (W1/W2) is between 1.2/1and 2/1. Other implementations are also contemplated.

In the illustrated system, a data write to any of the interlaced (e.g.,even-numbered data tracks) overwrites and effectively “trims” edges ofadjacent odd-numbered tracks. For example, the data track 504 overwritesedges of the data tracks 503 and 505 in narrow overlap regions where thedata of data tracks 503 and 505 “bleeds” over the natural trackboundaries. Consequently, data bits of the narrow data track 504 mayoverwrite the right-most edges of data bits of the wider written datatrack 503 and the left-most edges of data bits of the wider written datatrack 505. Even though each of the narrow written data tracks overwritesthe edge portions of data in the adjacent wider written data tracks, areadable portion of the data of the wider written tracks is retained inthe center region of each of the wider written data tracks. Therefore, abit error rate (BER) of the wider written data tracks 503 and 505 may besubstantially unaltered by the data write to the data track 504.

In at least one implementation, the wider written data tracks (e.g., theodd-numbered data tracks) include data stored at a different lineardensity than a linear density of data stored in the narrower writtendata tracks (e.g., even-numbered data tracks). This allows for anincrease in total ADC as compared to a system that uses a common lineardensity for a consecutive grouping of data tracks.

Notably, a random re-write of the data of one of the wider written datatracks (e.g., the data track 503) may overwrite and substantially affectreadability of data in adjacent even-numbered data tracks (e.g., thedata track 502). Therefore, a data management method utilizing PRA rulesis employed to ensure that groupings of adjacent data tracks are writtenin an order such that all data of all tracks are readable and totalread/write processing time is mitigated.

According to one implementation, a data management method includesmultiple phases, with different PRA rules applicable during each phase.The data management method may govern data writes to the entire magneticdisc 500, or (alternatively) govern data writes to a subset of themagnetic disc 500, such as a radial zone of the magnetic disc 500.

In a first phase, data is written exclusively to alternating tracks at ahigh linear density. For example, the odd-numbered data tracks with awide written track width may be written to sequentially, as illustratedby the notation “write 1”, “write 2”, “write 3” and “write 4” in FIG. 5.This first phase continues until a first capacity condition issatisfied. For example, the first capacity condition may be satisfiedwhen 50% of the data tracks in a region (e.g., a specific radial or zoneor the entire disc surface) store data. During this first phase of thedata management method, each of the odd-numbered data tracks can bewritten to at random and directly overwritten without re-writing anydata of adjacent data tracks.

After the first capacity condition is satisfied, a second phase of thedata management method commences. During the second phase of the datamanagement method, data writes may be directed to even-numbered datatracks. The even-numbered data tracks are written to at a lower lineardensity (e.g., narrower track width), and may be individually written atrandom (e.g., without re-writing data of any adjacent data tracks).

During the second phase, some odd-numbered data tracks may be written torandomly and others may not. For example, the data track 503 remainsrandomly writeable up until the point in time when data is first writtento either of adjacent data tracks 502 or 504. If an odd-numbered datatrack is bounded by a data track including data, the odd-numbered datatrack is no longer randomly writeable. For example, updating data of thedata track 503 may entail reading, caching, and subsequently re-writingthe data of the adjacent data tracks 502 and 504 (if 502 and 504 containdata).

In one implementation, every other even-numbered data track is leftblank for a period of time while the disk continues to fill up. Forexample, data is initially written to tracks 504 and 508 (per “write 5”and “write 6”, respectively), but no data is written to any of tracks502, 506, or 510. So long as every-other even-numbered data track isleft blank, non-random data writes entail writing no more than two datatracks at once. For example, overwriting the data track 503 entails (1)reading data track 502 to a temporary cache location; (2) writing thedata track 503; and (3) re-writing the data track 502 after the write ofdata track 503 is complete.

In some implementations, the data management method entails a thirdphase that commences once a second, different capacity condition issatisfied. For example, the third phase may commence after data isstored in all alternating even-numbered data tracks. A data managementmethod including a third phase of PRA is discussed with respect to FIG.5, below.

FIG. 6 illustrates data writes 600 employing another example PRA schemein an IMR system. During a first phase of the data management method,the controller directs the new incoming data sequentially to alternatingdata tracks (e.g., odd-numbered data tracks), such as in the orderdenoted by “write 1”, “write 2”, “write 3”, and “write 4.” Thecontroller continues filling the alternating data tracks with data inthis manner until a first capacity condition is satisfied. After thefirst capacity condition is satisfied, a second phase of the datamanagement method commences and the controller begins to direct newincoming data to every other even-numbered data track (e.g., via “write5” and “write 6,” as shown).

After a second capacity condition is satisfied, a third phase of thedata management method commences and the controller begins to directincoming data to the remaining un-filled data tracks (e.g., “write 7,”“write 8,” and “write 9”, as shown). For example, the second capacitycondition may be satisfied when the magnetic disc 600 stores data on 75%of the data tracks.

During the third phase of the data management method, a write operationto update a data track entails reading and writing no more than threedata tracks. For example, a write of the data track 605 entails (1)reading data tracks 604 and 606 to a temporary cache location; (2)writing the data track 605; and (3) subsequently re-writing the datatracks 604 and 606. Therefore, reading and writing data during the thirdphase results in higher performance loss that reading and writing dataduring the second and first phases. For example, writing data to thedata track 603 during the first phase may take a single revolution ofthe magnetic disc 600; however, during the third phase, writing data tothe data track 603 may take five revolutions of the magnetic disc 600(e.g., reading the data tracks 602 and 604 into a cache memory location,writing the data track 603, and then re-writing the data tracks 602 and603). Therefore, performance of the magnetic disc 600 is degraded by upto 80% more in the third phase than in the first phase.

One benefit of this multi-phase write management method is that manystorage drives may never be used in the third phase. For example, theaverage usage capacity of desktop hard drives may be between about 50%and 60%, allowing the storage drive to operate exclusively in the firstand second phases of the data write management method. Therefore, themulti-phase write management method greatly enhances performance inthese systems as compared to systems using SMR.

In FIG. 6, the data tracks written to in the first phase (e.g., theodd-numbered data tracks) have a first linear density and track width(W1); the data tracks written to in the second phase (e.g., the datatracks 602, 606, and 610) have a second linear density and track width(W2); and the data tracks written to in the third phase (e.g., the datatracks 604 and 608) have a third linear density and track width (W3). Inat least one implementation, the data tracks receiving the new data invarious different phases are of the same linear density and/or trackwidth. Thus, depending on the implementation, W2 may be the same ordifferent from W3 and the data track 604 may be of the same or adifferent linear density from the data track 602.

One consequence of the illustrated data management method is that anupdate of data to a single track never entails writing data to more thanthree data tracks (e.g., an odd-numbered data track and the two adjacenteven-numbered data tracks). This reduces back-end processing as comparedto shingled magnetic recording (SMR) systems that read and write data ingroups of “bands” including several (e.g., 10 or more) data tracks. Alsounlike shingled magnetic recording systems, the illustrated writemethodology allows for the narrow, alternating data tracks (e.g., theeven-numbered data tracks) to be written to at random (e.g., as asingle-track write) throughout the life of the drive, and forodd-numbered data tracks to be written to at random for least someperiod of time as the magnetic disc 600 is filled with data. Thus, thedisclosed system provides for a higher data rate and increased systemperformance as compared to SMR systems.

FIG. 7 illustrates an example multi-phase write management method forwriting to a region 700 of a magnetic storage medium of an IMR system.The region may be, for example, an entire surface of the magneticstorage medium, multiple surfaces of the magnetic storage medium, or aradial zone on the magnetic medium. During a first phase of the writemanagement method (as indicated by the notation “phase 1”), a storagedevice controller sequentially writes new data to a first series of datatracks defined by (2n+1), where n is an integer series n=[0, 1, 2, 3, 4. . . ]. Each data track in the first series of data tracks has awritten track width that is slightly wider than a defined track pitch716. Because the written track width is so wide, a linear density of thefirst series of data tracks may be higher than a linear density of othersubsequently written data tracks of narrower written width.

The storage device continues writing to data tracks in the series (2n+1)until a first capacity condition is satisfied. In one implementation,the first capacity condition is satisfied when 50% of all data tracks inthe region 700 include data. In another implementation, the capacitycondition is satisfied when a capacity of the region 700 reaches apredetermined threshold, such as 50-65% of a total capacity of theregion 700.

Once the first capacity condition is satisfied, a second phase of thewrite management method commences (as indicated by the notation “phase2”). During the second phase of the write management method, the storagedevice controller directs new data to a second series of data tracksdefined by (4n), including every-other even-numbered data track (e.g.,data tracks 4, 8, 12, etc.). Each data track in the second series ofdata tracks has a written track width that is equal to or slightly lessthan the defined track pitch 716. A linear density of the second seriesof data tracks (e.g., the 4n series) may be less than a linear densityof the first series of data tracks (e.g., the 2n+1 series). Therefore,each data track in the second series overwrites edges of data in theadjacent data tracks of the first series.

The storage device continues writing to data tracks in the series 4nuntil a second capacity condition is satisfied. The second capacitycondition may be satisfied when, for example, data is stored in about50-75% of data tracks in the region 700. Once the second capacitycondition is satisfied, a third phase of the write management methodcommences (as indicated by the notation “phase 3”). During the thirdphase of the write management method, the storage device controllerdirects new data to a third series of data tracks defined by (4n+2),including every fourth data track (e.g., data tracks 2, 6, 10, 14, etc.)on the storage medium or within a radial zone of the storage medium.

In one implementation, each data track in the third series of datatracks (the series 4n+2) has a written track width that is equal to orless than the written track width of data tracks in the second series. Alinear density of the third series of data tracks may be less than alinear density of the second series of data tracks (e.g., the 4n).

The storage device continues writing to data tracks in the third series(4n+2) until the region 700 reaches a maximum capacity (at or near 100%of an advertised capacity for the disc or for a particular radial zone).

FIG. 8 illustrates another example five-phase write management forwriting to a region 800 of a magnetic storage medium of an IMR system.The region may be, for example, an entire surface of the magneticmedium, multiple surfaces of the magnetic medium, or a radial zone onthe magnetic medium. During a first phase of the write management method(as indicated by the notation “phase 1”), a storage device controllersequentially writes new data to a first series of data tracks defined by(2n+1), where n is an integer series n=[0, 1, 2, 3, 4 . . . ]. Forexample, the first capacity condition may be satisfied when data isstored in about 50% of data tracks in the region 800.

Once the first capacity condition is satisfied, a second phase of thewrite management method commences (as indicated by the notation “phase2”). During the second phase of the write management method, the storagedevice controller directs new data to a second series of data tracksdefined by (8n), including every 8^(th) data track in the consecutiveseries of data tracks (e.g., the data tracks 8, 16, 24, etc).

The storage device continues writing to data tracks in the series 8nuntil a second capacity condition is satisfied. The second capacitycondition may be satisfied when, for example, data is stored in about50-62.5% of data tracks in the region 800.

Once the second capacity condition is satisfied, a third phase of thewrite management method commences (as indicated by the notation “phase3”). During the third phase of the write management method, the storagedevice controller directs new data to a third series of data tracksdefined by (8n+4), including the data tracks 4, 12, 20, etc.

The storage device continues writing to data tracks in the third series8n+4 until a third capacity condition is satisfied. The third capacitycondition may be satisfied when, for example, data is stored in about62.5-75% in the region 800.

Once the third capacity condition is satisfied, a fourth phase of thewrite management method commences (as indicated by the notation “phase4”). During the fourth phase of the write management method, the storagedevice controller directs new data to a fourth series of data tracksdefined by (8n+2), including the data tracks 2, 10, 18, 26, etc. Thestorage device continues writing to data tracks in the fourth series8n+2 until a fourth capacity condition is satisfied. The fourth capacitycondition may be satisfied when, for example, data is stored in about75-87% of data tracks in the region 800.

Once the fourth capacity condition is satisfied, a fifth phase of thewrite management method commences (as indicated by the notation “phase5”). During the fifth phase of the write management method, the storagedevice controller directs new data to a third series of data tracksdefined by (8n+6), including the data tracks 6, 14, 22, etc. The storagedevice continues writing to data tracks in the fifth series 8n+6 untilthe maximum capacity of the region 800 is attained.

Each individual series of data tracks (e.g., the series 2n+1, 8n, 8n+4,8n+2, 8n+6) have a same density and track width. For example, the datatracks defined by 2n+1 (phase 1) have a first linear density and trackwidth, the data tracks defined by 8n have a second linear density andtrack width, etc. In one implementation, the written track width and/orlinear density of each series of data tracks decreases in the followingorder: phase 1 (2n+1 series); phase 2 (8n series); phase 3 (8n+4series); phase 4 (8n+2 series); phase 5 (8n+6 series). In still otherimplementations, data tracks in two or more of the various series have asame linear density and track width. By varying linear densities ofdifferent orders of interlaced traced, higher areal density capacitiescan be achieved.

Still other implementations may implement additional high-orders ofinterlaced magnetic recording than those shown in FIG. 7 or 8. Forexample, another implementation may manage the interlaced data in seriesdefined by: 16n, 16n+8, 16n+4, 16n+12, 16n+2, 16n+6, 16n+10, and 16n+14.

FIG. 9 illustrates example operations for employing a PRA scheme in anIMR system. A first direction operation 905 directs writes of new,incoming data to a first series of data tracks on the storage medium.Each data track in the first series of data tracks is separated from theother data tracks in the first series by one or more interlaced datatracks.

After a first capacity condition is satisfied, a second directionoperation 910 directs incoming writes of new data to a second series ofdata tracks interlaced with the first series of data tracks. Accordingto one implementation, the second series of data tracks has a narrowertrack width and includes data of a lower linear density than the firstseries of data tracks.

After a second capacity condition is satisfied, yet another directionoperation 912 directs incoming writes of new data to a third series ofdata tracks interlaced with both the first and the second series of datatracks. The data written to the third series of data tracks may be at asame or a different linear density and/or track width than the data ofthe second series of data tracks. In one implementation, the thirdseries of data tracks has a narrower track width and includes data of alower linear density than the second series of data tracks.

FIG. 10 illustrates example operations 1000 for employing another PRAscheme. The example operations 1000 may be implemented in any type ofmagnetic recording device including without limitation CMR and IMRdevices.

A write operation 1005 writes data to a first series of data tracksuntil a capacity condition is satisfied. The first series of data tracksare each separated from one another by at least one interlaced datatrack. For example, the first series of data tracks may be alternatingdata tracks and tracks interlaced with the alternating data tracks areleft blank until the first capacity condition is satisfied. The capacitycondition may be, for example, a predetermined number of data tracksstoring data within the region, a threshold capacity of the region, etc.

So long as the capacity is not satisfied (e.g., capacity of the regionis below a threshold), the magnetic recording device does not performany post-write scan operations such as incrementing or resetting writecounters and/or performing DOSs to verify integrity of stored data. Oncethe capacity condition is satisfied, an enabling operation 1010 enablespost-write scan operations.

When the post-write scan operations are enabled, a write operation toany particular data track increases a write counter associated with eachimmediately adjacent data track. When the write counter for a particulardata track exceeds a threshold, the data track is subjected to a DOS.The DOS reads data of the data track and determines whether a number ofcorrectable read errors satisfies an error threshold. If the number ofcorrectable read errors satisfies the error threshold, the storagedevice controller re-writes the data of that data track and resets thewrite counter of the data track to a default starting value.

The embodiments of the disclosed technology described herein areimplemented as logical steps in one or more computer systems. Thelogical operations of the presently disclosed technology are implemented(1) as a sequence of processor-implemented steps executing in one ormore computer systems and (2) as interconnected machine or circuitmodules within one or more computer systems. The implementation is amatter of choice, dependent on the performance requirements of thecomputer system implementing the disclosed technology. Accordingly, thelogical operations making up the embodiments of the disclosed technologydescribed herein are referred to variously as operations, steps,objects, or modules. Furthermore, it should be understood that logicaloperations may be performed in any order, adding and omitting asdesired, unless explicitly claimed otherwise or a specific order isinherently necessitated by the claim language.

The above specification, examples, and data provide a completedescription of the structure and use of exemplary embodiments of thedisclosed technology. Since many embodiments of the disclosed technologycan be made without departing from the spirit and scope of the disclosedtechnology, the disclosed technology resides in the claims hereinafterappended. Furthermore, structural features of the different embodimentsmay be combined in yet another embodiment without departing from therecited claims.

What is claimed is:
 1. A method comprising: writing data to a firstseries of data tracks within a region of a storage medium while apost-write scan operation is disabled and until a first capacitycondition is satisfied, the data tracks of the first series eachseparated from one another by at least one interlaced data track; andonce the capacity condition is satisfied, enabling the post-write scanoperation to verify integrity of adjacent track data after a subsequentwrite operation.
 2. The method of claim 1, wherein the first series ofdata tracks is a series of alternating data tracks.
 3. The method ofclaim 1, wherein enabling the post-write scan procedure furthercomprises: enabling a data track write counter to increment for a firstdata track each time data is recorded in a second data track directlyadjacent to the first data track.
 4. The method of claim 3, furthercomprising: reading data of the first data track when a value of thedata track write counter satisfies an increment threshold.
 5. The methodof claim 3, further comprising: if a number of read errors of the firstdata track data satisfies an error threshold, re-writing the data of thefirst data track and resetting the data track write counter.
 6. Themethod of claim 1, wherein the capacity condition is satisfied when atleast half of the data tracks in the region store data.
 7. The method ofclaim 1, wherein the region is an entire surface of a magnetic media. 8.The method of claim 1, wherein the region is a radial zone on themagnetic media.
 9. Apparatus comprising: a storage device controllerconfigured to: write data to a first series of data tracks within aregion of a storage medium while a post-write scan operation is disabledand until a first capacity condition is satisfied, the data tracks ofthe first series each separated from one another by at least oneinterlaced data track; and once the capacity condition is satisfied,enable the post-write scan operation to verify integrity of adjacenttrack data after a subsequent write operation.
 10. The apparatus ofclaim 9, wherein the first series of data tracks is a series ofalternating data tracks.
 11. The apparatus of claim 9, wherein enablingthe post-write scan procedure further comprises: enabling a data trackwrite counter to increment for a first data track each time data isrecorded in a second data track directly adjacent to the first datatrack.
 12. The apparatus of claim 11, further comprising: reading dataof the first data track when a value of the data track write countersatisfies an increment threshold.
 13. The apparatus of claim 9, furthercomprising: if a number of read errors of the first data track datasatisfies an error threshold, re-writing the data of the first datatrack and resetting the data track write counter.
 14. The apparatus ofclaim 9, wherein the capacity condition is satisfied when at least halfof the data tracks in the region store data.
 15. The apparatus of claim9, wherein the region is an entire surface of a magnetic media.
 16. Theapparatus of claim 9, wherein the region is a radial zone on themagnetic media.
 17. One or more tangible computer-readable storage mediaencoding computer-executable instructions for executing on a computersystem a computer process, the computer process comprising: writing datato a first series of data tracks within a region of a storage mediumwhile a post-write scan operation is disabled and until a first capacitycondition is satisfied, the data tracks of the first series eachseparated from one another by at least one interlaced data track; andonce the capacity condition is satisfied, enabling the post-write scanoperation to verify integrity of adjacent track data after a subsequentwrite operation.
 18. The one or more tangible computer-readable storagemedia of claim 17, wherein the first series of data tracks is a seriesof alternating data tracks.
 19. The one or more tangiblecomputer-readable storage media of claim 17, wherein enabling thepost-write scan procedure further comprises: enabling a data track writecounter to increment for a first data track each time data is recordedin a second data track directly adjacent to the first data track. 20.The one or more tangible computer-readable storage media of claim 19,wherein the computer process further comprises: reading data of thefirst data track when a value of the data track write counter satisfiesan increment threshold.